Pipe Coupling Having Movable Gripping Bodies

ABSTRACT

A coupling for securing pipe elements together in end-to-end relation is disclosed. The coupling has segments joined end-to-end by adjustable connection members. The segments surround a central space which receives the pipe elements. One or more gripping bodies are captured between the segments. The gripping bodies are arranged opposite to each other. When the segments are drawn toward each other by the connection members, interaction between the reaction surfaces and the contact surfaces forces the gripping bodies radially inwardly. Inwardly facing arcuate surfaces on the segments and the gripping bodies engage and retain the pipe elements.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/470,522, filed May 14, 2012, which is a divisional of U.S. patentapplication Ser. No. 13/113,124, filed May 23, 2011, now U.S. Pat. No.8,177,263, which is a divisional of U.S. patent application Ser. No.12/119,661 filed May 13, 2008, now U.S. Pat. No. 7,950,701 which isbased on and claims priority to U.S. Provisional Patent Application No.60/938,003, filed May 15, 2007, all of which are hereby incorporated byreference herein.

FIELD OF THE INVENTION

This invention relates to couplings for joining pipe elements inend-to-end relationship.

BACKGROUND OF THE INVENTION

Mechanical couplings for joining pipe elements end-to-end findwidespread use throughout a broad spectrum of industries such as thechemical industry, the petroleum industry and mining, as well as inmunicipal water service and fire suppression systems for buildings andother structures.

An example of a prior art coupling currently in use is provided in U.S.Pat. No. 7,086,131, which discloses a coupling having a pair of couplingsegments joined end-to-end by fasteners received in lugs at each end ofthe segments. A sealing member is positioned between the segments. Thecoupling is pre-assembled at the factory. The segments are designed andsized to receive pipe elements in the field which are inserted directlybetween the coupling segments in the pre-assembled state, without theneed to disassemble and reassemble the coupling. After insertion of thepipe elements, the fasteners are tightened to effect a fluid-tight,mechanically restrained joint between the pipe elements.

While it is advantageous to pre-assemble such couplings because it savestime and thereby cost during construction, power tools are often used totighten the fasteners for convenience, as they are faster and lessfatiguing. Power tools are of limited value, however, where no source ofelectrical power or compressed air is available, even those tools whichare battery operated. Furthermore, power tools which cause electricalsparking may not be used in environments, such as mines, where explosiveconditions may exist. It would be advantageous to provide a pipecoupling which can be pre-assembled (and thereby secure the costadvantages and convenience of such couplings) while being easilymanually tightened by workmen installing the couplings. It is furtheradvantageous to decrease the stiffness of the joint formed by thecoupling for certain applications. This can be accomplished by employingcouplings according to the invention.

SUMMARY OF THE INVENTION

The invention concerns a pipe coupling for securing end portions of apair of pipe elements together end-to-end. In one embodiment, thecoupling comprises a plurality of segments connectable end-to-endsurrounding a central space for receiving the pipe elements. Eachsegment has a pair of arcuate surfaces positioned in spaced relation,the arcuate surfaces facing the central space and being engagable withthe pipe elements. Connection members are positioned at opposite ends ofeach of the segments for adjustably connecting the segments to oneanother. The connection members are adjustably tightenable for drawingthe segments toward one another and into engagement with the pipeelements. Respective reaction surfaces are positioned on at least two ofthe connection members which face one another. The reaction surfacesface the central space. At least one gripping body is positioned betweentwo of the segments. The gripping body has a pair of gripping surfacespositioned in spaced apart relation. The gripping surfaces face thecentral space for engagement with the pipe elements. A first pair ofcontact surfaces is positioned on the gripping body in facing relationwith the reaction surfaces. Adjustable tightening of the connectionmembers draws the coupling segments together. The contact surfacesinteract with the reaction surfaces to move the gripping body into thecentral space for engagement of the gripping surfaces with the pipeelements.

In one embodiment, the reaction surfaces are angularly oriented withrespect to the projections. Orientation angles for the reaction surfacesfrom about 30° to about 60° are feasible, with 45° being preferred.Alternately, the reaction surfaces may have a convex shape. The contactsurfaces may also angularly oriented with respect to the projections.Orientation angles for the contact surfaces from about 30° to about 60°are feasible, with 45° being preferred. Alternately, the contactsurfaces may have a convex shape.

In one embodiment of the coupling, the contact surfaces project radiallyoutwardly away from the central space. In another embodiment, thegripping bodies have a second pair of contact surfaces. The first andsecond pairs of contact surfaces are positioned on opposite sides of thegripping body.

In another embodiment, the coupling comprises a plurality of segmentsconnectable end-to-end surrounding a central space for receiving thepipe elements. Each segment has a pair of arcuate surfaces in spacedrelation. The arcuate surfaces face the central space and are engagablewith the pipe elements. Connection members are positioned at oppositeends of each of the segments for adjustably connecting the segments toone another. The connection members are adjustably tightenable fordrawing the coupling segments toward one another and into engagementwith the pipe elements. First and second reaction surfaces arepositioned at opposite ends of each coupling segment in spaced relation.The reaction surfaces face the central space. First and second grippingbodies are positioned between the segments at opposite ends thereof.Each of the gripping bodies has a pair of gripping surfaces positionedin spaced relation to each other. The gripping surfaces face the centralspace and are engagable with the pipe elements. Each of the grippingbodies has a plurality of contact surfaces positioned in spacedrelation. Each of the contact surfaces is engaged with one of thereaction surfaces of the segments. Each of the gripping bodies has endfaces positioned opposite to one another. The segments have inwardlyprojecting shoulders positioned adjacent to the reaction surfaces. Theshoulders are engagable with the end faces. Either the end faces or theshoulders or both are angularly oriented so as to cause rotation of thegripping bodies about an axis substantially perpendicular to the pipeelements when the coupling segments are drawn together. Adjustabletightening of the connection members draws the coupling segmentstogether. The contact surfaces interact with the reaction surfaces tomove the gripping bodies radially inwardly for engagement of thegripping surfaces with the pipe elements.

In one embodiment, the reaction surfaces extend in a tangentialdirection of the segments. In another embodiment, the gripping bodiescomprise a channel adapted to receive a sealing member. The channel isskewed relatively to the gripping surfaces so as to substantially alignwith the sealing member upon rotation of the gripping bodies.

Another embodiment of the pipe coupling according to the inventioncomprises a plurality of segments connectable end-to-end. The segmentssurround a central space. Each segment has first and second arcuategrooves in spaced relation facing the central space. Connection membersare positioned at opposite ends of each of the segments for adjustablyconnecting the segments to one another. The connection members areadjustably tightenable for drawing the segments toward one another.First and second reaction surfaces are positioned at opposite ends ofeach coupling segment in spaced relation to one another. The reactionsurfaces face the central space. First and second gripping bodies arepositioned between the segments at opposite ends thereof. Each of thegripping bodies has first and second arcuate grooves positioned inspaced relation. The grooves face the central space. Each of thegripping bodies has a plurality of contact surfaces positioned in facingrelation with the reaction surfaces. Each of the contact surfaces isengaged with one of the reaction surfaces on each of the segments. Firstand second retainers are received within the grooves of the couplings.Each of the retainers comprises an annular band having a plurality ofteeth extending radially inwardly. Each annular band is split so as topermit radial motion of the teeth when the band is radially compressed.The first retainer is received within the first grooves in the couplingsegments and the gripping bodies and the second retainer is receivedwithin the second grooves in the coupling segments and the grippingbodies. The teeth of the first retainer are angularly oriented towardthe teeth of the second retainer, and the teeth of the second retainerare angularly oriented toward the teeth of the first retainer.Adjustable tightening of the connection members draws the couplingsegments together. The contact surfaces interact with the reactionsurfaces to move the gripping bodies radially inwardly for compressingthe retainers into engagement with the pipe elements. Preferably, thereaction surfaces extend in a tangential direction of the segments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded isometric view of an embodiment of a couplingaccording to the invention;

FIGS. 2 and 3 are cross-sectional views of the coupling shown in FIG. 1;

FIG. 4 is an isometric view of the coupling shown in FIG. 1;

FIGS. 4A and 4B are isometric views of alternate embodiments of acoupling according to the invention;

FIG. 5 is an exploded isometric view of another embodiment of a couplingaccording to the invention;

FIGS. 6 and 7 are elevational views of the coupling shown in FIG. 5;

FIG. 8 is an isometric view of the coupling shown in FIG. 5;

FIG. 9 is an isometric exploded view of another coupling embodimentaccording to the invention;

FIG. 10 is a front view of a component of the coupling shown in FIG. 9;

FIG. 11 is an isometric view of the coupling shown in FIG. 9;

FIG. 12 is a sectional view taken at line 12-12 of FIG. 11;

FIGS. 13 and 14 are sectional views of the coupling shown in FIG. 9;

FIG. 15 is an exploded view of another embodiment of the couplingaccording to the invention;

FIG. 16 is an exploded view of another embodiment of the couplingaccording to the invention; and

FIG. 17 is a sectional view of a portion of the coupling shown in FIG.16.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows an exploded isometric view of a coupling embodiment 10according to the invention. Coupling 10 comprises a plurality ofsegments 12 and 14. Segments 12 and 14 are connectable end-to-end tosurround a central space 16. Connection of the segments is effected byconnection members 18 positioned at opposite ends of each of thesegments 12 and 14. In this embodiment, the connection members compriseprojections 20 which extend outwardly from the ends of the segments.Projections 20 have apertures 22 adapting them to receive fasteners,such as bolts 24 and nuts 26. The fasteners are adjustably tightenableand cooperate with the projections 20 for drawing the segments 12 and 14toward the central space 16 upon tightening.

Each segment has a pair of arcuate surfaces 28. Surfaces 28 arepositioned in spaced relation to one another and face the central space16. The arcuate surfaces engage and retain pipe elements 30 (see FIG. 4)when the fasteners connecting projections 20 are tightened to draw thesegments toward each other. The arcuate surfaces may engagecircumferential grooves in the pipe elements, plain ended pipe elements,flared end pipe elements or pipe ends having a shoulder.

Each segment also has at least one, but preferably a plurality of,reaction surfaces 32 positioned on the connection members 18. In theembodiment shown in FIG. 1, two reaction surfaces 32 are positioned oneach projection 20. The reaction surfaces are angularly oriented withrespect to the projections, and may have an orientation angle 34 fromabout 30° to about 60° and are inclined so as to face the central space16. Orientation angles of about 45° are preferred as explained below.

Coupling 10 also comprises one or more gripping bodies. In the exampleembodiment, two gripping bodies 36 and 38 are positioned between thesegments 12 and 14 opposite to one another. Each gripping body has apair of gripping surfaces 40. Similar to the arcuate surfaces 28, thegripping surfaces are positioned in spaced apart relation and face thecentral space 16. Each gripping body has a pair of contact surfaces 42positioned in facing relation with the reaction surfaces 32 on theprojections 20 of the segments 12 and 14. The contact surfaces are alsoangularly oriented with respect to the projections, and may have anorientation angle 44 from about 30° to about 60°. Orientation angles ofabout 45° are preferred as explained below. Preferably, the orientationangles 34 and 44 are complementary to one another, meaning that theyhave approximately the same angular orientation.

Upon assembly of the coupling 10, a seal 46 is captured within thecentral space 16 by the segments 12 and 14 and the gripping bodies 36.Seal 46 ensures that the coupling 10 provides a fluid-tight jointbetween pipe ends. The seal 46 is sized so that, in an undeformed state,its outer circumference 48 supports the segments 12 and 14 and thegripping bodies 36 and 38 in spaced apart relation sufficient for pipeelements to be inserted into the central space 16 without disassemblingthe coupling.

Operation of the coupling is described with reference to FIGS. 2 and 3.FIG. 2 shows the coupling 10 as received from the factory in thepre-assembled state, installation ready. In this configuration, thefasteners are not yet tightened, thereby allowing the segments 12 and 14and the gripping bodies 36 and 38 to be positioned radially outwardlyaway from the central space 16 to allow pipe elements (not shown forclarity) to be inserted into the central space. As noted above, the seal46 is sized to hold the segments and gripping bodies radially outwardlyto facilitate pipe insertion. Upon insertion, the pipe elements engagethe seal 46 which provides fluid tightness to the joint. Next, the bolts24 and nuts 26 are tightened, drawing the segments 12 and 14 toward oneanother and the central space 16. As the segments move, the arcuatesurfaces 28 are brought into engagement with the outer surface of thepipe elements to retain them in the coupling. As shown in FIG. 3, motionof the segments 12 and 14 toward one another causes the gripping bodies36 and 38 to move inwardly toward the central space 16, in a directionsubstantially perpendicular to the motion of the segments. This permitsthe gripping surfaces 40 on the gripping bodies 36 and 38 to also engagethe outer surface of the pipe elements. Motion of the gripping bodiestoward the central space 16 is effected by the interaction of thecontact surfaces 42 on the gripping bodies with the reaction surfaces 32on the projections 20. The angular orientation 44 and 34 of the contactsurfaces and the reaction surfaces respectively, allows the forcesbetween the surfaces to be resolved into a component directed toward thecentral space. This force, applied at the contact surfaces, causes themotion of the gripping bodies toward the central space. As noted above,orientation angles of about 45° are preferred for both the reactionsurfaces and the contact surfaces. The 45° angles ensure that, duringthe motion of the segments 12 and 14 and the gripping bodies 36 and 38toward the central space 16, the arcuate surfaces 28 and the grippingsurfaces 40 are at all times equidistant from the pipe elements 30 andcontact the pipe elements substantially simultaneously.

As shown in FIG. 2, there are multiple gaps 17 between the end faces 19of the gripping bodies 36, 38, and shoulders 21 on segments 12 and 14.The gaps 17 allow for the relative motion between the gripping bodes andthe segments. The gaps are about one half the size of gaps betweensegments in prior art couplings and consequently the gripping bodies andsegments have less tendency to pinch the seal 46 as the gaps 17 close tovirtually line on line contact as shown in FIG. 3. This results in moreuniform compression of seal 46 and the elimination of extrusion pathsfor the seal when under pressure.

It is advantageous to position the reaction surfaces 32 on theprojections 20 and have the contact surfaces 42 project substantiallyradially outwardly away from the central space 16 so that the interfacebetween the contact surfaces and the reaction surfaces is near thefastener (bolt 24, nut 26) which joins the connections members 18 (inthis example projections 20) to one another. Internal pressure withinthe coupling 10, acting on the seal 46, will force the segments 12 and14 and the gripping bodies 36 and 38 away from the central space. Forceapplied to the gripping bodies within the coupling is transmitted to thesegments at the interface between the contact surfaces 42 and thereaction surfaces 32. Due to their angular orientation, the contactsurfaces will tend to act like a wedge and force the projections 20apart. By placing the interface close to the fastener joining theprojections, the separation of the projections will be less than if theinterface were farther from the fastener. The advantageous positioningof the contact surface-reaction surface interface minimizes theseparation of the segments and allows the coupling to withstand higherpressures without leaking. Furthermore, by placing the reaction forcesbetween the segments and the gripping bodies near the fasteners thedistortion of the segments by the gripping bodies is lessened and thecoupling better maintains its round shape.

FIG. 4A illustrates another embodiment 11 of a coupling according to theinvention. In this embodiment, the contact surfaces 42 on the grippingbodies 36 and 38 have a convex shape. This permits them to engage thereaction surfaces 32 tangentially when the segments 12 and 14 are drawntoward one another, resulting in reaction forces which cause motion ofthe gripping bodies toward the central space. The reaction surfaces 32are angularly oriented. FIG. 4B shows another embodiment 13 wherein thereaction surfaces 32 have a convex shape and the contact surfaces 42 areangularly oriented. This again allows for tangential engagement betweenthe reaction surfaces and the contact surfaces, resulting in reactionforces which cause motion of the gripping bodies toward the centralspace as the segments 12 and 14 are drawn toward each other.

FIG. 5 shows an isometric exploded view of another coupling embodiment50 according to the invention. Coupling 50 has gripping bodies 36 and 38with contact surfaces 52 positioned on opposite sides of the grippingbodies. Again, the contact surfaces are angularly oriented with respectto the connection members 18 and interface with reaction surfaces 54positioned on the connection members 18. Orientation angles 56 for thecontact surfaces from about 30° to about 60° are advantageous for thiscoupling design. It is preferred that the orientation angle of thereaction surfaces 54 be approximately the same as the contact surfacesas shown in FIG. 8.

Operation of coupling 50 is similar to that of coupling 10 describedabove. As shown in FIG. 6, before tightening of fasteners 58 thesegments 12 and 14 and the gripping bodies 36 and 38 are spacedoutwardly away from the central space 16 so as to allow a pipe elementto be inserted into the central space. Tightening of the fasteners asshown in FIG. 7 draws the segments 12 and 14 toward one another and thecentral space, allowing the arcuate surfaces 28 to engage the pipeelements' outer surface. Interaction between the contact surfaces 52 onthe gripping bodies 36 and 38 and the reaction surfaces 54 on thesegments 12 and 14 forces the gripping bodies to move inwardly towardthe central space as the fasteners 58 are tightened. The inward motionof the gripping bodies allows their gripping surfaces 40 to engage thepipe elements 30 as shown in FIG. 8.

FIG. 9 shows an exploded view of another coupling embodiment 60according to the invention. Coupling 60 comprises coupling segments 12and 14. The segments are arranged in facing relation and are joinedend-to-end by connection members 18 positioned at opposite ends of eachsegment. In this embodiment, as with those previously described, theconnection members comprise outwardly extending projections 20 whichreceive fasteners 58 that are adjustably tightenable. Tightening of thefasteners draws the coupling segments 12 and 14 toward one another andthe central space 16.

Each segment has inwardly facing arcuate surfaces 28 positioned inspaced relation to one another. The arcuate surfaces occupy positionsbetween the ends of each segment. Reaction surfaces 32 are positioned inspaced relation at opposite ends of each coupling segment 12 and 14. Thereaction surfaces face inwardly toward the central space 16 and extendin a tangential direction around the segments. The reaction surfaces areangularly oriented as described below.

Gripping bodies 36 and 38 are positioned between the segments 12 and 14at opposite ends of the coupling 60. Each gripping body has inwardlyfacing gripping surfaces 40 arranged in spaced relation. Preferably, thegripping surfaces 40 align with respective arcuate surfaces 28 when thecoupling is assembled as best shown in FIG. 11. With reference again toFIG. 9, each gripping body has contact surfaces 42 in spaced relation.Contact surfaces 42 face outwardly away from the central space 16 andengage respective reaction surfaces 32 on the segments 12 and 14. Thecontact surfaces on the gripping bodies cooperate with the reactionsurfaces on the segments such that, when the segments are drawn towardone another, for example, by the tightening of fasteners 58, thegripping bodies are urged radially inwardly as explained further below.

A seal 46 is positioned between the coupling segments 12 and 14 and thegripping bodies 36 and 38. Both the segments and gripping bodies haverespective channels 62 and 64 positioned between the arcuate surfaces 28and the gripping surfaces 40 which receive the seal. The innercircumference 66 of the seal 46 has inwardly facing sealing surfaces 68and 70 which engage pipe elements joined by the coupling to form afluid-tight seal. The seal 46 is sized so that, in an undeformed state,its outer circumferences 72 supports the segments 12 and 14 and thegripping bodies 36 and 38 in spaced apart relation sufficient for pipeelements to be inserted into the central space 16 without disassemblingthe coupling. Preferably, the sealing member is a ring formed of anelastic, resilient material such as EPDM elastomer which deforms whenthe coupling segments are drawn toward one another by adjustablytightening the connection members 18.

FIG. 11 shows the pipe coupling 60 in its pre-assembled state ready foruse. To effect a fluid-tight joint connecting pipe elements inend-to-end relation, pipe elements 30 are inserted into the sealingmember 46 as shown in FIG. 12, so that the segments straddle facing endportions of the pipe elements. The pipe elements are inserted to anextent such that grooves 74 in the outer surfaces of the pipe elementsalign with the arcuate surfaces of the segments (not shown) and thegripping surfaces 40 of the gripping bodies 36 and 38. Insertion of thepipe elements to the proper depth may be facilitated by a pipe stop 76positioned on the sealing member between the sealing surfaces 68 and 70.The pipe stop projects inwardly to engage the ends of the pipe elementsand limit the insertion depth as desired.

FIG. 13 shows a cross-sectional view of the coupling 60 with pipeelement 30 inserted. Attention is drawn to the reaction surfaces 32 onsegments 12 and 14 engaging the contact surfaces 42 on gripping bodies36 and 38. The reaction surfaces are angularly oriented so that when thefasteners 58 are tightened, drawing the segments 12 and 14 toward oneanother as shown in FIG. 14, the gripping bodies 36 and 38 are movedradially inwardly so that the gripping surfaces on the gripping bodiesengage and grip the grooves 74 of the pipe elements 30 shown in FIG. 12.The motion of the segments 12 and 14 toward one another also causes thearcuate surfaces 28 (not shown) on each segment to engage and grip thegrooves as well. The pipe elements are, thus, secured in end-to-endrelation. The sealing member is deformed radially inwardly to force thesealing surfaces 68 and 70 into further engagement with the outersurfaces of the pipe elements. This configuration produces a relativelyrigid joint. A more flexible joint can alternately be provided if themotion of the arcuate surfaces is limited so that they do not engage andclamp the floor of the groove. To this end, the travel of the grippingbodies is limited by the extent or length of the reaction surfaces andthe contact surfaces. Limitation of motion of the arcuate surfaces onthe segments toward the central space is preferably controlled bylimiting the motion of the segments through contact of the connectionmembers 18.

As noted, the coupling embodiment 60 provides a substantially rigidjoint for the pipe elements, i.e., the joint has significant stiffnessabout all three axes (bending, axial extension and torsion) to preventsignificant angular deflection as well as axial movement (compressionand extension) of the pipe elements relatively to one another. Torsionaldeflections are also inhibited. The rigidity of the joint is effected bythe angularly oriented surfaces 78 and 80 positioned on each segment 12and 14 adjacent to the connection members 18 as best shown in FIG. 9.The surfaces 78 and 80 on each segment have opposite slopes and are infacing relation with the angularly oriented surfaces on the adjoiningsegment. When the segments 12 and 14 are drawn toward one another bytightening of fasteners 58, the angularly oriented surfaces on eachsegment engage one another and force the segments to rotate in oppositedirections about an axis 82, perpendicular to the pipe elements joinedby the coupling. The rotation of the segments causes the arcuatesurfaces 28 to forcibly engage the sidewalls of the grooves in the pipeelements and stiffen the joint, as described in U.S. Pat. Nos.4,611,839, 4,639,020 and 5,758,907 hereby incorporated by reference.

To further enhance the rigidity of the joint between pipe elementsformed by coupling 60, the gripping bodies 36 and 38 may be designed asshown in FIG. 9 such that their end faces 84 and 86 are angularlyoriented relative to the gripping surfaces 40. The angular orientationis best shown in FIG. 10 for gripping body 36 which takes on arhomboidal profile as a result. The end faces 84 and 86 engage inwardlyprojecting shoulders 88 on each segment 12 and 14 as the segments aredrawn toward one another when forming a joint. The angular orientationof the end faces causes the gripping bodies 36 and 38 to rotate inopposite directions about an axis 90 as they are brought into contactwith the shoulders 88. Axis 90 is substantially perpendicular to thepipe elements being joined by the coupling segments 12 and 14. Therotation of the gripping bodies causes the gripping surfaces 40 thereonto rotate and forcibly engage the sidewalls of the grooves in the pipeelements similar to the arcuate surfaces on the segments. To avoidrotationally deforming the seal 46, the channels 64 in each grippingbody are skewed in the opposite direction of rotation so that, when thegripping elements rotate about axis 90, the channels 64 will align withthe sealing members so that essentially only radial compression results,i.e., there is no significant twisting of the sealing member about axis90.

It is further observed that the angular orientation of the end faces 84and 86 causes rotation of the segments 12 and 14 about axis 82, therebyrendering the sloped surfaces 78 and 80 optional, and useful to enhancethe rotation of the segments if necessary.

Rotation of the gripping bodies 36 and 38 about axis 90 may also beachieved by angularly orienting the inwardly projecting shoulders 88 asshown in FIG. 15, the orientation angle 92 of the shoulder forcingrotation of the gripping bodies as the segments 12 and 14 are drawntogether, forcing engagement between the shoulders 88 and the end faces84 and 86 of the gripping bodies. It is also possible to combine thefeatures of FIGS. 9 and 15 and have both the end faces 84 and 86angularly oriented as well as the shoulders 88.

It is also feasible to provide angularly oriented surfaces on eachsegment which have opposite slopes. Such couplings will also provide arigid joint, but the interaction of the surfaces causes the couplings toslide in opposite directions and thereby engage the sidewalls of thegrooves. If it is desired to allow some degree of bending flexibility tothe joint, the surfaces adjacent to the connection members are made withno slope, i.e., substantially flat.

FIG. 16 shows an exploded view of another coupling embodiment 94according to the invention. Coupling 94 is used to couple plain end pipeelements together, i.e., pipes having no grooves, beads, enlargements orother features near the ends to facilitate engagement with the coupling.Many of the components of this embodiment are similar to coupling 60 andwill not be described in detail. Note also that the sealing member 46shown in FIG. 1 is not shown in FIG. 6 for clarity, although the same ora similar sealing member is also used with coupling 94.

To enable the coupling 94 to grip plain end pipe elements, two retainers96 and 98 are used. Each retainer comprises an annular band 100 whichhas a plurality of flexible, resilient teeth 102. The teeth projectradially inwardly for engagement with the pipe elements as describedbelow. The teeth are also angularly oriented out of the plane of theband 100, with the teeth on retainer 96 being angled toward the teeth onretainer 98 and vice versa. The angular orientation of the teeth allowsthe pipe elements to be inserted into the coupling, but prevents thepipe elements from being withdrawn when the teeth forcibly engage thepipe elements as described below. Band 100 is split, as evidenced by thegap 104. This gap permits the band to be compressed radially to allowthe teeth to engage the pipe elements.

The retainers are received within grooves 106 and 108 in segments 12 and14 and grooves 110 and 112 in the gripping bodies 36 and 38. Preferably,when assembled, the grooves in the segments align with the grooves inthe gripping bodies. As shown with reference to FIGS. 16 and 17, whenthe pipe elements 30 are inserted into the coupling 94 and the fasteners58 are tightened, the segments 12 and 14 are drawn together and thegripping bodies 36 and 38 move inwardly in response to the interactionof the reaction surfaces 32 with the contact surfaces 42. The inwardmotion of the grooves 106, 108, 110 and 112 compresses the bands 100 ofretainers 96 and 98 inwardly so that teeth 102 engage the surfaces ofpipe elements 30. Because the teeth are angled they deflect inwardly andpermit the pipe elements to be inserted into the coupling. But whenforce is applied which tends to remove the pipe elements from thecoupling, the teeth prevent this motion due to the self-jammingcharacteristics of the angled teeth.

Retainers 96 and 98 preferably have a plurality of tabs 114 whichproject outwardly from the band 100. As shown in FIG. 16, the tabsengage the grooves 106 and 108 of the segments as well as grooves 110and 112 of the gripping bodies and provide a degree of radialflexibility to the retainer. This added flexibility permits the segmentsto be joined in what is known as “pad-to-pad” relation wherein theconnection members 18 on the segments abut one another when thefasteners 58 are tightened in spite of dimensional variations in thesegments and pipes. It is advantageous that the segments join pad-to-padas it provides a readily identifiable visual indication that thefasteners are fully tightened and thereby avoids the need for torquingthe fasteners to a particular value as proof of completion of afluid-tight joint. Avoiding the need for torque measurements simplifiesinstallation of the coupling, as a torque wrench is not necessary.

Couplings according to the invention realize an advantage through theuse of the moving gripping bodies which allows them to be installed fromthe pre-assembled state easily using hand tools. The movable grippingbodies reduce the torque required to bring the segments together andgrip the pipe elements to effect a fluid-tight joint.

What is claimed is:
 1. A pipe coupling for securing end portions of apair of pipe elements together end-to-end, said coupling comprising: aplurality of segments connectable end-to-end surrounding a central spacehaving a center, said central space for receiving said pipe elements,each said segment having a pair of arcuate surfaces positioned in spacedrelation, said arcuate surfaces facing said central space and beingengagable with said pipe elements; connection members positioned atopposite ends of each of said segments for adjustably connecting saidsegments to one another, said connection members being adjustablytightenable for drawing said segments toward one another and intoengagement with said pipe elements; respective reaction surfacespositioned on at least two of said connection members facing oneanother, said reaction surfaces facing said central space and beingangularly oriented with respect to said connection members; a grippingbody positioned between two of said segments, said gripping body havinga pair of gripping surfaces positioned in spaced apart relation andfacing said center of said central space; a first pair of contactsurfaces positioned on said gripping body in facing relation with saidreaction surfaces, said contact surfaces having a convex shape; andwherein adjustable tightening of said connection members draws saidcoupling segments together, said contact surfaces interacting with saidreaction surfaces to move said gripping body into said central space forengagement of said gripping surfaces with said pipe elements.
 2. A pipecoupling according to claim 1, wherein said connection members comprisea pair of projections extending outwardly from the ends of saidsegments, said projections being adapted to receive fasteners foradjustably connecting said segments to one another, said fasteners beingadjustably tightenable for drawing said arcuate surfaces of saidsegments into engagement with said pipe elements.
 3. A pipe couplingaccording to claim 1, wherein said reaction surfaces are oriented at anangle from about 30° to about 60°.
 4. A pipe coupling according to claim1, wherein said reaction surfaces are oriented at an angle of about 45°.5. A pipe coupling according to claim 1, wherein said contact surfacesproject radially outwardly away from said central space.
 6. A pipecoupling according to claim 1, further comprising a second pair ofcontact surfaces, said first and second pairs of contact surfaces beingpositioned on opposite sides of said gripping body.
 7. A pipe couplingaccording to claim 1, further comprising a sealing member capturedbetween said segments and positioned between said arcuate surfaces, saidsealing member having inwardly facing sealing surfaces engagable withsaid pipe elements for forming a fluid-tight joint between said pipeelements.
 8. A pipe coupling for securing end portions of a pair of pipeelements together end-to-end, said coupling comprising: a plurality ofsegments connectable end-to-end surrounding a central space having acenter, said central space for receiving said pipe elements, each saidsegment having a pair of arcuate surfaces positioned in spaced relation,said arcuate surfaces facing said central space and being engagable withsaid pipe elements; connection members positioned at opposite ends ofeach of said segments for adjustably connecting said segments to oneanother, said connection members being adjustably tightenable fordrawing said segments toward one another and into engagement with saidpipe elements; respective reaction surfaces positioned on at least twoof said connection members facing one another, said reaction surfacesfacing said central space and having a convex shape; a gripping bodypositioned between two of said segments, said gripping body having apair of gripping surfaces positioned in spaced apart relation and facingsaid center of said central space; a first pair of contact surfacespositioned on said gripping body in facing relation with said reactionsurfaces, said contact surfaces being angularly oriented with respect tosaid connection members; and wherein adjustable tightening of saidconnection members draws said coupling segments together, said contactsurfaces interacting with said reaction surfaces to move said grippingbody into said central space for engagement of said gripping surfaceswith said pipe elements.
 9. A pipe coupling according to claim 8,wherein said connection members comprise a pair of projections extendingoutwardly from the ends of said segments, said projections being adaptedto receive fasteners for adjustably connecting said segments to oneanother, said fasteners being adjustably tightenable for drawing saidarcuate surfaces of said segments into engagement with said pipeelements.
 10. A pipe coupling according to claim 8, wherein said contactsurfaces are oriented at an angle from about 30° to about 60°.
 11. Apipe coupling according to claim 8, wherein said contact surfaces areoriented at an angle of about 45°.
 12. A pipe coupling according toclaim 8, wherein said contact surfaces project radially outwardly awayfrom said central space.
 13. A pipe coupling according to claim 8,further comprising a second pair of contact surfaces, said first andsecond pairs of contact surfaces being positioned on opposite sides ofsaid gripping body.
 14. A pipe coupling according to claim 8 furthercomprising a sealing member captured between said segments andpositioned between said arcuate surfaces, said sealing member havinginwardly facing sealing surfaces engagable with said pipe elements forforming a fluid-tight joint between said pipe elements.
 15. A pipecoupling for securing end portions of a pair of pipe elements togetherend-to-end, said coupling comprising: a pair of segments connectableend-to-end surrounding a central space having a center, said centralspace for receiving said pipe elements, each said segment having a pairof arcuate surfaces positioned in spaced relation, said arcuate surfacesfacing said central space and being engagable with said pipe elements;connection members positioned at opposite ends of each of said segmentsfor adjustably connecting said segments to one another, said connectionmembers being adjustably tightenable for drawing said segments towardone another and into engagement with said pipe elements; a respectivereaction surface positioned on each of said connection members facingone another, said reaction surfaces facing said central space and beingangularly oriented with respect to said connection members; a pair ofgripping bodies positioned between said segments, said gripping bodieseach having a pair of gripping surfaces positioned in spaced apartrelation and facing said center of said central space; a first pair ofcontact surfaces positioned on each of said gripping bodies in facingrelation with said reaction surfaces, said contact surfaces having aconvex shape; and wherein adjustable tightening of said connectionmembers draws said coupling segments together, said contact surfacesinteracting with said reaction surfaces to move said gripping bodiesinto said central space for engagement of said gripping surfaces withsaid pipe elements.
 16. A pipe coupling according to claim 15, whereinsaid connection members comprise a pair of projections extendingoutwardly from the ends of said segments, said projections being adaptedto receive fasteners for adjustably connecting said segments to oneanother, said fasteners being adjustably tightenable for drawing saidarcuate surfaces of said segments into engagement with said pipeelements.
 17. A pipe coupling according to claim 15, wherein saidreaction surfaces are oriented at an angle from about 30° to about 60°.18. A pipe coupling according to claim 15, wherein said reactionsurfaces are oriented at an angle of about 45°.
 18. A pipe couplingaccording to claim 15, wherein said contact surfaces project radiallyoutwardly away from said central space.
 20. A pipe coupling according toclaim 15, further comprising a second pair of contact surfaces, saidfirst and second pairs of contact surfaces being positioned on oppositesides of said gripping body.
 21. A pipe coupling according to claim 15,further comprising a sealing member captured between said segments andpositioned between said arcuate surfaces, said sealing member havinginwardly facing sealing surfaces engagable with said pipe elements forforming a fluid-tight joint between said pipe elements.
 22. A pipecoupling for securing end portions of a pair of pipe elements togetherend-to-end, said coupling comprising: a pair of segments connectableend-to-end surrounding a central space having a center, said centralspace for receiving said pipe elements, each said segment having a pairof arcuate surfaces positioned in spaced relation, said arcuate surfacesfacing said central space and being engagable with said pipe elements;connection members positioned at opposite ends of each of said segmentsfor adjustably connecting said segments to one another, said connectionmembers being adjustably tightenable for drawing said segments towardone another and into engagement with said pipe elements; a respectivereaction surface positioned on each of said connection members facingone another, said reaction surfaces facing said central space and havinga convex shape; a pair of gripping bodies positioned between saidsegments, said gripping bodies each having a pair of gripping surfacespositioned in spaced apart relation and facing said center of saidcentral space; a first pair of contact surfaces positioned on each ofsaid gripping bodies in facing relation with said reaction surfaces,said contact surfaces being angularly oriented with respect to saidconnection members; and wherein adjustable tightening of said connectionmembers draws said coupling segments together, said contact surfacesinteracting with said reaction surfaces to move said gripping bodiesinto said central space for engagement of said gripping surfaces withsaid pipe elements.
 23. A pipe coupling according to claim 22, whereinsaid connection members comprise a pair of projections extendingoutwardly from the ends of said segments, said projections being adaptedto receive fasteners for adjustably connecting said segments to oneanother, said fasteners being adjustably tightenable for drawing saidarcuate surfaces of said segments into engagement with said pipeelements.
 24. A pipe coupling according to claim 22, wherein saidcontact surfaces are oriented at an angle from about 30° to about 60°.25. A pipe coupling according to claim 22, wherein said contact surfacesare oriented at an angle of about 45°.
 26. A pipe coupling according toclaim 22, wherein said contact surfaces project radially outwardly awayfrom said central space.
 27. A pipe coupling according to claim 23,further comprising a second pair of contact surfaces, said first andsecond pairs of contact surfaces being positioned on opposite sides ofsaid gripping body.
 28. A pipe coupling according to claim 22 furthercomprising a sealing member captured between said segments andpositioned between said arcuate surfaces, said sealing member havinginwardly facing sealing surfaces engagable with said pipe elements forforming a fluid-tight joint between said pipe elements.